Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Total revenues	$ 2,744	$ 2,696	$ 6,258	$ 6,060
Depreciation and amortization	418	354	831	702
Operating income/(loss)	458	426	1,244	1,180
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	58	19	116	38
Operating income/(loss)	72	24	83	33
Con Edison Transmission
Segment Reporting Information [Line Items]
Operating income/(loss)	(2)	(1)	(3)	(3)
CECONY
Segment Reporting Information [Line Items]
Total revenues	2,331	2,338	5,371	5,222
Depreciation and amortization	339	316	673	626
Operating income/(loss)	376	382	1,101	1,087
CECONY | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	261	243	518	483
Operating income/(loss)	314	318	571	571
CECONY | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	56	51	111	100
Operating income/(loss)	94	82	438	404
CECONY | Steam
Segment Reporting Information [Line Items]
Depreciation and amortization	22	22	44	43
Operating income/(loss)	(32)	(18)	92	112
O&R
Segment Reporting Information [Line Items]
Depreciation and amortization	21	19	42	38
Operating income/(loss)	13	23	67	68
O&R | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	15	14	30	28
Operating income/(loss)	16	18	31	26
O&R | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	6	5	12	10
Operating income/(loss)	(3)	5	36	42
Operating segment
Segment Reporting Information [Line Items]
Total revenues	2,744	2,696	6,258	6,060
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Total revenues	233	158	450	391
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Total revenues	1	1	2	2
Operating segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	2,331	2,338	5,371	5,222
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	1,833	1,807	3,630	3,536
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	408	435	1,330	1,276
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	90	96	411	410
Operating segment | O&R
Segment Reporting Information [Line Items]
Total revenues	179	198	437	445
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Total revenues	138	144	283	293
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Total revenues	41	54	154	152
Other
Segment Reporting Information [Line Items]
Total revenues	0	1	(2)	0
Depreciation and amortization	0	0	0	0
Operating income/(loss)	(1)	(2)	(4)	(5)
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	(23)	(24)	(47)	(49)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	5	4	9	8
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	2	2	3	4
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	$ 16	$ 18	$ 35	$ 37